The present invention relates to a method for making a bisphenol, such as bisphenol A(BPA), by the condensation of a phenol, and a ketone in the presence of a sulfonated aromatic organic polymer, such as a polystyrene ion-exchange resin having chemically combined aminoorganomercaptan groups. More particularly, the present invention relates to a condensation reaction between acetone and a phenol reactant which has been initially fed through an ion-exchange "guard bed" in the form of a sulfonated polystyrene ion-exchange resin having chemically combined aminoorganomercaptan groups, prior to the subsequent condensation of the phenol with acetone.
As discussed in British patent 1,183,564, which is incorporated herein by reference, an improvement can be achieved in the synthesis of bisphenol A by the condensation of phenol with acetone, if an ion-exchange catalyst is used which contains sulfonic acid groups. As shown by Pressman et al., U.S. Pat. No. 4,584,416 which is incorporated herein by reference, an ion-exchange resin in the form of a sulfonated polystyrene having ionically bound aminoorganomercaptan groups can be used as a catalyst to make bisphenol. As used hereinafter, the expression "chemically combined" which is sometimes used with reference to aminoorganomercaptan groups, means that these groups can be either ionically or covalently bound to the backbone of the sulfonated aromatic organic polymeric resin. As taught by Pressman et al., improved acetone conversion and p,p-bisphenol A selectivity can be achieved with the use of sulfonated aromatic organic polymeric ion-exchange resin having chemically combined aminoorganomercaptan groups Experience has shown however, that the activity of a sulfonated polystyrene ion-exchange resins having such chemically combined aminoorganomercaptan groups is often adversely affected over a period of time. A reduction in chemically combined aminoorganomercaptan, or "thiol" groups can result. A possible explanation of the loss of thiol groups in the sulfonated polystyrene resin is that the phenol which is used in the condensation reaction with acetone can be contaminated with greater than 1 ppm of hydroxyacetone (HA). The hydroxyacetone has been found to directly react with aminoorganomercaptan groups to form a substantially stable species having reduced catalytic activity. As a result, a dramatic decrease in rate of bisphenol A production can result over a period of time.
It would be desirable therefore to maintain the activity of the bisphenol condensation catalyst. It also would be desirable to minimize the deactivation of chemically combined aminoorganomercaptan groups and achieve a satisfactory rate of bisphenol production.